High-speed networks are continually evolving. The evolution includes a continuing advancement in the operational speed of the networks. The network implementation of choice that has emerged is Ethernet networks physically connected over unshielded twisted pair wiring. Ethernet in its 10/100 BASE-T form is one of the most prevalent high speed LANs (local area network) for providing connectivity between personal computers, workstations and servers.
High-speed LAN technologies include 100 BASE-T (Fast Ethernet) and 1000 BASE-T (Gigabit Ethernet). Fast Ethernet technology has provided a smooth evolution from 10 Megabits per second (Mbps) performance of 10 BASE-T to the 100 Mbps performance of 100 BASE-T. Gigabit Ethernet provides 1 Gigabit per second (Gbps) bandwidth with essentially the simplicity of Ethernet. There is a desire to increase operating performance of Ethernet to even greater data rates.
FIG. 1 shows a block diagram of a pair of Ethernet transceivers communicating over a bi-directional transmission channel, according to the prior art. An exemplary transmission channel includes four pairs of copper wire 112, 114, 116, 118. The transceiver pair can be referred to as link partners, and includes a first Ethernet port 100 and a second Ethernet port 105. Both of the Ethernet ports 100, 105 include four transmitter Tx, receiver Rx, and I/O buffering sections corresponding to each of the pairs of copper wires 112, 114, 116, 118.
The twisted copper wires can operate as antennas that are susceptible to receive electromagnetic interference (EMI). Generally, EMI appears as a narrowband interference source to Ethernet receivers. Ethernet systems mostly rely on EMI protection that is provided by shielding, and by transmitting the information differentially to provide immunity against the common-mode characteristics of the EMI. Higher frequency EMI is also rejected by the filtering performed at the analog-front-end (AFE) of the Ethernet receiver. In the past, Ethernet systems have had sufficient operating margin such that the EMI did not cause the link to fail. However, the protection provided by current Ethernet systems is not sufficient and EMI can cause the link to fail and unable to receive data.
In Ethernet systems, after AFE processing of the receive signal, the signal is converted to a digital representation for further processing. Removing the EMI in the digital domain requires the transceiver to have an AFE and digital processing capabilities that allow it to process and convert the expected receive signal plus EMI signal into a digital representation without any additional distortion because of the presence of the EMI signal. Since the EMI signal can be large compared to the receive signal, digital mitigation of EMI requires more analog and digital resources to be able to handle and process a larger overall receive signal without introducing any new distortion or degradation. This increases the transceiver's complexity, area, power, and cost. Moreover, the addition of a large EMI signal to the receive signal can result in clipping and/or saturation, resulting in signal distortion and leading to link performance degradation.
It is desirable to have an apparatus and method for suppressing electromagnetic interference in a receive signal of Ethernet systems that addresses the above-described issues. It is additionally desirable to suppress components of transmit signals in the receive signal.